Subject: Re: TradeTriggers@TDA; INTRADAY % price drops
Interactive Brokers does, and a seemingly limitless number of other customizable conditional/dependent algorithms.

https://www.interactivebrokers...

I've had trouble with the learning curves for some of them - even had to make "trial trades" to make sure some worked as I wanted.
Though they do have lots of live & recorded Order Type seminars [of course I've never tried one :-)].

:-)Shawn